Bug#37671 crash on prepared statement + cursor + geometry + too many open files!
if mysql_execute_command() returns error then free materialized_cursor object.
is_rnd_inited is added to satisfy rnd_end() assertion
(handler may be uninitialized in some cases)


sql/sql_cursor.cc:
  if mysql_execute_command() returns error then free materialized_cursor object.
  is_rnd_inited is added to satisfy rnd_end() assertion
  (handler may be uninitialized in some cases)
sql/sql_select.cc:
  added result check
tests/mysql_client_test.c:
  test case